Tin oxide overcoat indium tin oxide coatings, coated glazings, and production methods

ABSTRACT

The invention provides transparent conductive coatings based on indium tin oxide. The coating has a tin oxide overcoat. In some embodiments, the coating further includes one or more overcoat films comprising silicon nitride, silicon oxynitride, or silica. The coating and its films have compositions, thicknesses, and properties that simultaneously produce low sheet resistance and high visible transmission, preferably together with neutral color properties and good durability.

PRIORITY

This application is a continuation-in-part of U.S. Utility application Ser. No. 14/185,287, filed on Feb. 20, 2014, which is a continuation of U.S. Utility application Ser. No. 13/006,992, filed on Jan. 14, 2011 and now issued as U.S. Pat. No. 8,658,262, which claims priority to U.S. Provisional Application No. 61/295,694, filed on Jan. 16, 2010.

FIELD OF THE INVENTION

The present invention relates to thin film coatings for glass and other substrates. In particular, this invention relates to transparent electrically conductive coatings based on indium tin oxide. Also provided are methods and equipment for producing such coatings and glazing assemblies.

BACKGROUND OF THE INVENTION

A variety of transparent electrically conductive oxide (TCO) coatings are known in the art. Commonly, these coatings include an indium tin oxide film. In some cases, the indium tin oxide film is located beneath one or more overcoat films of silicon nitride, silicon oxynitride, or silicon dioxide. It would be desirable to provide an overcoat film that: (i) has a composition different from that of the TCO film, and yet (ii) contains a metal also found in the TCO film. It would be particularly desirable to provide an overcoat film of this nature that provides the coating with exceptional durability and adheres particularly well to indium tin oxide film and any overcoat films of silicon nitride, silicon oxynitride, or silicon dioxide. In such cases, it would be desirable for the coating and its films to have compositions and thicknesses that simultaneously achieve low sheet resistance and high visible transmission, preferably together with neutral color properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a broken-away schematic cross-sectional view of a substrate having a major surface bearing a transparent electrically conductive coating in accordance with certain embodiments of the present invention;

FIG. 2 is a broken-away schematic cross-sectional view of a substrate having a major surface bearing a transparent electrically conductive coating in accordance with other embodiments of the invention;

FIG. 3 is a broken-away schematic cross-sectional view of a substrate having a major surface bearing a transparent electrically conductive coating in accordance with still other embodiments of the invention;

FIG. 4 is a broken-away schematic cross-sectional view of a substrate having a major surface bearing a transparent electrically conductive coating in accordance with yet other embodiments of the invention;

FIG. 5 is a partially broken-away schematic cross-sectional side view of a multiple-pane insulating glazing unit that includes an exterior pane and an interior pane, the interior pane having a fourth surface carrying a transparent electrically conductive coating in accordance with certain embodiments of the invention;

FIG. 6 is a partially broken-away schematic cross-sectional side view of a multiple-pane insulating glazing unit that includes an exterior pane and an interior pane, the exterior pane having a first surface carrying a transparent electrically conductive coating, and the interior pane having a fourth surface carrying another transparent electrically conductive coating, in accordance with certain embodiments of the invention;

FIG. 7 is a partially broken-away schematic cross-sectional side view of a multiple-pane insulating glazing unit that includes an exterior pane and an interior pane, the exterior pane having a first surface carrying a hydrophilic and/or photocatalytic film, and the interior pane having a fourth surface carrying a transparent electrically conductive coating, in accordance with certain embodiments of the invention; and

FIG. 8 is a partially broken-away schematic cross-sectional side view of a multiple-pane insulating glazing unit that includes an exterior pane and an interior pane, the exterior pane having a second surface carrying a low-emissivity coating, and the interior pane having a fourth surface carrying a transparent electrically conductive coating, in accordance with certain embodiments of the invention.

SUMMARY OF THE INVENTION

Certain embodiments of the invention provide a multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces. A desired one of the two external pane surfaces bears a coating comprising both an indium tin oxide film and a tin oxide film. The tin oxide film is located over the indium tin oxide film.

In some embodiments, the invention provides a coated pane comprising a glass substrate and a coating on the glass substrate. The coating comprises both an indium tin oxide film and a tin oxide film. The tin oxide film is located further from the glass pane than is the indium tin oxide film. In the present embodiments, the indium tin oxide film has a thickness of between 100 Å and 2,000 Å, while the tin oxide film has a thickness of between 90 Å and 1,200 Å. Preferably, the indium tin oxide film has a sheet resistance of less than 20 ohms/square, while the coated pane has a visible transmission of greater than 75%.

Some embodiments provide a multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces. A desired one of the two external pane surfaces bears a coating comprising both an indium tin oxide film and a tin oxide film. The tin oxide film is located over the indium tin oxide film. In the present embodiments, the indium tin oxide film has a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 Å and 1,600 Å. Preferably, the tin oxide film has a thickness of between 90 Å and 1,200 Å, and is devoid of indium oxide. In the present embodiments, the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that has only one film comprising silver. The film comprising silver contains at least 50% silver by weight. The low-emissivity coating is exposed to the between-pane space. The multiple-pane insulating glazing unit has a U value of less than 0.25 together with a visible transmission of greater than 75%, and the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 0 and a “b_(h)” color coordinate of between −8 and −1.

Certain embodiments provide a multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces. A desired one of the two external pane surfaces bears a coating comprising both an indium tin oxide film and a tin oxide film. The tin oxide film is located over the indium tin oxide film. In the present embodiments, the indium tin oxide film has a sheet resistance of less than 20 ohms/square, and a thickness of between 1,000 Å and 1,600 Å. Preferably, the tin oxide film has a thickness of between 90 Å and 1,200 Å, and is devoid of indium oxide. In the present embodiments, the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that has only two films comprising silver. Each of the two films comprising silver contains at least 50% silver by weight. The low-emissivity coating is exposed to the between-pane space. The multiple-pane insulating glazing unit has a U value of less than 0.25 together with a visible transmission of greater than 65%, and the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 0 and a “b_(h)” color coordinate of between −8 and −1.

Further, some embodiments provide a multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces. A desired one of the two external pane surfaces bears a coating comprising both an indium tin oxide film and a tin oxide film. The tin oxide film is located over the indium tin oxide film. In the present embodiments, the indium tin oxide film has a sheet resistance of less than 20 ohms/square, and a thickness of between 1,000 Å and 1,600 Å. Preferably, the tin oxide film has a thickness of between 90 Å and 1,200 Å, and is devoid of indium oxide. In the present embodiments, the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that includes three films comprising silver. Each of the films comprising silver contains at least 50% silver by weight. The low-emissivity coating is exposed to the between-pane space. The multiple-pane insulating glazing unit has a U value of less than 0.25 together with a visible transmission of greater than 60%, and the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 1 and a “b_(h)” color coordinate of between −7 and −1.

Still further, certain embodiments of the invention provide a coated pane comprising a glass substrate and a coating on the glass substrate. The coating includes both an indium tin oxide film and a tin oxide film. The tin oxide film is located further from the glass pane than is the indium tin oxide film. In the present embodiments, the coating has an emissivity in the range of from 0.25 to 0.55, and the coated pane has a visible transmission of greater than 75%. Preferably, the indium tin oxide film has a thickness of greater than 100 Å but less than 1,100 Å, and the tin oxide film has a thickness of between 90 Å and 1,200 Å.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is to be read with reference to the drawings, in which like elements in different drawings have like reference numerals. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Skilled artisans will recognize that the examples provided herein have many useful alternatives that fall within the scope of the invention.

Many embodiments of the invention involve a coated substrate. A wide variety of substrate types are suitable for use in the invention. In some embodiments, the substrate is a sheet-like substrate having generally opposed first and second major surfaces. For example, the substrate can be a sheet of transparent material (i.e., a transparent sheet). The substrate, however, is not required to be a sheet, nor is it required to be transparent.

For many applications, the substrate will comprise a transparent (or at least translucent) material, such as glass or clear plastic. For example, the substrate is a glass sheet (e.g., a window pane) in certain embodiments. A variety of known glass types can be used, such as soda-lime glass. In some cases, it may be desirable to use “white glass,” a low iron glass, etc. In certain embodiments, the substrate is part of a window, door, skylight, or other glazing. Depending on the level of solar control desired, the present coating may be applied to tinted glass. Thus, the coating of any embodiment disclosed herein can optionally be provided on a sheet of tinted glass. This may provide particularly good selectivity.

Substrates of various sizes can be used in the present invention. Commonly, large-area substrates are used. Certain embodiments involve a substrate having a major dimension (e.g., a length or width) of at least about 0.5 meter, preferably at least about 1 meter, perhaps more preferably at least about 1.5 meters (e.g., between about 2 meters and about 4 meters), and in some cases at least about 3 meters. In some embodiments, the substrate is a jumbo glass sheet having a length and/or width that is between about 3 meters and about 10 meters, e.g., a glass sheet having a width of about 3.5 meters and a length of about 6.5 meters. Substrates having a length and/or width of greater than about 10 meters are also anticipated.

Substrates of various thicknesses can be used in the present invention. In some embodiments, the substrate (which can optionally be a glass sheet) has a thickness of about 1-8 mm. Certain embodiments involve a substrate with a thickness of between about 2.3 mm and about 4.8 mm, and perhaps more preferably between about 2.5 mm and about 4.8 mm. In one particular embodiment, a sheet of glass (e.g., soda-lime glass) with a thickness of about 3 mm is used.

The substrate 10′ has opposed surfaces 16 and 18, which preferably are opposed major surfaces. In some cases, surface 16 is destined to be an internal surface exposed to a between-pane space of an insulating glazing unit, while surface 18 is destined to be an external surface exposed to an interior of a building. This, however, will not be the case in all embodiments.

As shown in FIGS. 1 and 2, the substrate 10′ bears a transparent electrically conductive coating 7. In FIG. 1, the coating 7 includes, in sequence from surface 18 outwardly, an indium tin oxide film 20 and a tin oxide film 100. In FIG. 2, the coating 7 includes, from surface 18 outwardly, an optional base film 15, the indium tin oxide film 20, and the tin oxide film 100. The films 15, 20, and 100 can be provided in the form of discrete layers, thicknesses of graded film, or a combination of both including at least one discrete layer and at least one thickness of graded film. While the base film 15 is shown as a single layer, it can alternatively be a plurality of layers. Preferably, all the films in the coating 7 are oxide, nitride, or oxynitride films. In some cases, all the films in the coating 7 are sputtered films.

The coating 7 preferably is formed of materials, and made by a process (as detailed herein), that allows the coated substrate to have a haze level of less than 0.5 or less than 0.3 (e.g., less than 0.2, less than 0.1, or even less than 0.09), a roughness R_(a) of less than about 10 nm, less than about 5 nm, or less than about 3 nm (e.g., less than about 2 nm), and a monolithic visible transmission of greater than 75% (preferably greater than 80%).

Haze can be measured in well-known fashion, e.g., using a BYK Haze-Gard plus instrument. Reference is made to ASTM D 1003-00: Standard Test method for Haze and Luminous Transmittance of Transparent Plastics, the contents of which are incorporated herein by reference.

In certain embodiments, the coated substrate has a haze of less than 0.3 and a surface roughness of about less than 3 nm, together with a monolithic visible transmission of greater than 70% (e.g., before and after heat treatment), greater than 73% (e.g., before and after heat treatment), greater than 81% (e.g., after heat treatment), greater than 82% (e.g., after heat treatment), or even greater than 85% in some cases (e.g., after heat treatment), in combination with a post-heat R_(sheet) of less than 75 ohms/square, less than 55 ohms/square, less than 30 ohms/square, less than 15 ohms/square, or in some cases even less than 13 ohms/square, such as about 11.5 to 12.5 ohms/square.

The coating 7 also has a low surface roughness. Preferably, the coating 7 has a surface roughness R_(a) of less than 10 nm, less than 5 nm, less than 3 nm, less than 2.5 nm, less than 2.2 nm, or even less than 2.0 nm, such as about 1.9 nm. The deposition method and conditions preferably are chosen so as to provide the coating with such a roughness. Alternatively, the coating could be polished after deposition to reduce its surface roughness. Preferably, though, the coating exhibits the preferred surface roughness without requiring any polishing or the like (e.g., as-deposited).

Surface roughness is defined in terms deviations from the mean surface level. The surface roughness R_(a) is the arithmetical mean surface roughness. This is the arithmetic average of the absolute deviations from the mean surface level. The arithmetical mean surface roughness of a coating is commonly represented by the equation: R_(a)=1/L∫₀ ^(L)|ƒ(x)|dx.” The surface roughness R_(a) can be measured in conventional fashion, e.g., using an Atomic Force Microscope (AFM) equipped with conventional software that gives R_(a).

When provided, the optional base film 15 can comprise, consist essentially of, or consist of silica, alumina, or a mixture of both. In other embodiments, the base film 15 comprises titanium dioxide. In still other embodiments, the base film 15 comprises tin oxide (e.g., SnO₂). In such embodiments, the base film 15 may be devoid of indium. For example, a base film 15 consisting of (or at least consisting essentially of) tin oxide is provided in some cases. Combinations of two or more of silica, alumina, titanium dioxide, and tin oxide may be used as well. Alternatively, other dielectric films may be used.

Thus, in certain embodiments, in addition to the indium tin oxide film 20, the coating 7 includes a film 15 comprising tin oxide located under the indium tin oxide film 20 in combination with a tin oxide film 100 located over the indium tin oxide film 20.

The indium tin oxide film 20 comprises indium tin oxide optionally together with one or more other materials. If desired, zinc, aluminum, antimony, fluorine, carbon nanotubes, or other additives can be included in the film. Preferably, the indium tin oxide film 20 consists essentially of, or consists of, indium tin oxide. The indium tin oxide film 20 can contain various relative percentages of indium oxide and tin oxide. Indium oxide is the major constituent. That is, it accounts for more than 50% of the film's total weight. Preferably, the composition of the film ranges from about 75% indium oxide/25% tin oxide to about 95% indium oxide/5% tin oxide, such as about 90% indium oxide/10% tin oxide.

The tin oxide film 100 is located over the indium tin oxide film 20. In some cases, the tin oxide film 100 comprises fluorine. Preferably, the tin oxide film 100 is devoid of indium oxide. For example, the tin oxide film 100 may consist of (or at least consist essentially of) tin oxide (e.g., SnO₂). In certain embodiments, film 100 contains at least 75% tin oxide, at least 85% tin oxide, or at least 95% tin oxide (based on the total weight of the film), while also being devoid of indium oxide.

The coating 7 can optionally include a nitride film between the indium tin oxide film and the tin oxide film. The nitride film may comprise one or more of silicon nitride, aluminum nitride, and titanium nitride. For example, a thin film of silicon nitride can optionally be positioned directly between (i.e., so as to contact both) the indium tin oxide film and the tin oxide film. When provided, this silicon nitride film (which can optionally include a small amount of aluminum) may have a thickness of less than 250 Å, or even less than 200 Å, e.g., about 150 Å.

In other embodiments, the tin oxide film 100 is in contact with the indium tin oxide film 20. Providing the tin oxide film 100 directly over (i.e., so as to be in contact with) the underlying indium tin oxide film 20 can be advantageous in that, while these two films have different compositions, both contain tin oxide and may provide exceptional adhesion to each other. This film combination may also make the coating particularly smooth, thus creating a coated surface that is easier to clean, remove label residue, etc.

When provided, the optional base film 15 has a thickness of 50 Å or more, such as about 70-300 Å. In certain embodiments, the coating includes a base film of silica (optionally including some aluminum), alumina, titanium dioxide, or tin oxide at a thickness of 75-150A.

In other embodiments, the indium tin oxide film 20 is directly on (i.e., in contact with) the substrate surface 18. In these embodiments, there is of course no base film 15. Applicant has found that good results can be achieved in cases where indium tin oxide film is directly on soda-lime float glass.

Preferably, the indium tin oxide film 20 has a thickness of between 100 Å and 2,000 Å. In certain embodiments, the indium tin oxide film 20 has a thickness of less than 1,750 Å, such as between 1,000 Å and 1,600 Å, or even less than 1,500 Å, such as about 1,200-1,400 Å. The thicknesses recited herein are physical thicknesses unless otherwise specified to be optical thicknesses.

The indium tin oxide film 20 preferably has a sheet resistance of less than 55 ohms/square. In certain embodiments, the sheet resistance is less than 20 ohms/square, or even less than 15 ohms/square, such as about 11.5-12.5 ohms/square.

The tin oxide film 100 can have a thickness of between 90 Å and 1,200 Å. In certain embodiments, the film 100 has a thickness of between 100 Å and 600 Å, such as between 200 Å and 400 Å, e.g., about 350 Å.

Some embodiments provide the thickness of the indium tin oxide film 20 in the range of about 1,100-1,500 Å in combination with the thickness of the tin oxide film 100 being about 100-700 Å. This combination of thicknesses, however, is not required for all embodiments. Rather, this combination of thicknesses is merely used in one group of embodiments. This combination of thicknesses, however, can optionally be provided in any embodiment hereof (i.e., in any embodiment having any of the noted combinations of other features and properties described herein).

Table 1 below shows four exemplary film stacks that can be used as coating 7 (here, it will be appreciated that the tin oxide film is the outermost film of the coating):

TABLE 1 FILM SAMPLE A SAMPLE B SAMPLE C SAMPLE D ITO 1,325 Å 1,250 Å 1,240 Å 1,350 Å SnO₂  440 Å  560 Å  600 Å  460 Å

These film stacks represent a broader group of embodiments wherein the coating 7 has a total thickness of less than 2,400 Å. A base film (e.g., silica at about 100 Å) can optionally be added. Additionally or alternatively, a nitride film (e.g., silicon nitride at about 150 Å) may be added between the ITO and SnO₂ films.

The coating 7 can optionally further include an oxynitride film 90 located over the tin oxide film 100. Reference is made to FIG. 3. When provided, the oxynitride film 90 can have a thickness of between 100 Å and 1,300 Å, such as between 400 angstroms and 900 angstroms. The oxynitride film 90 can optionally be directly over (i.e., so as to contact) the tin oxide film 100. The oxynitride film 90 may comprise aluminum, oxygen, and nitrogen. In certain embodiments, the oxynitride film 90 is an exposed outermost film of the coating 7.

In some cases, the oxynitride film 90 comprises silicon oxynitride at a thickness of between 400 Å and 900 Å. The silicon oxynitride may, for example, be sputter deposited from one or more silicon-aluminum targets, such as elemental targets comprising a sputterable material consisting of about 83% silicon and 17% aluminum.

In certain embodiments, the coating 7 includes a film comprising titanium oxide 70. When provided, the film comprising titanium oxide 70 can be located over the tin oxide film 100. Furthermore, when both the optional oxynitride film 90 and the optional film comprising titanium oxide 70 are provided, the film comprising titanium oxide is located over the oxynitride film. In preferred embodiments, the film comprising titanium oxide 70 has a thickness of less than 200 Å, such as from 10-75 Å, e.g., about 50 Å.

Preferably, the film comprising titanium oxide 70 is photocatalytic, hydrophilic, or both. Suitable films are described in U.S. Pat. No. 7,294,404 and Ser. No. 11/129,820 and U.S. Pat. Nos. 7,713,632 and 7,604,865 and Ser. No. 11/293,032 and U.S. Pat. Nos. 7,862,910 and 7,820,309 and 7,820,296, the salient teachings of each of which are incorporated herein by reference.

In some embodiments, the coated substrate 10′ is part of a monolithic glazing. In other embodiments, the coated substrate 10′ is part of a multi-pane insulating glazing unit (“IG unit”) 110.

In one group of embodiments, the coating 7 is on a #4 surface, a #6 surface, or another external surface of the inboard pane of an IG unit 100. By providing the transparent electrically conductive coating 7 on this surface, the temperature of this indoor pane under certain conditions can be decreased. In such cases, by providing a photocatalytic and/or hydrophilic film comprising titanium oxide 70 over the rest of the coating 7, any condensation that may occur on the room-side surface may be more readily formed into a sheet and evaporated.

Thus, certain embodiments provide a coated substrate (e.g., a glass pane) having the following films in sequence moving outwardly from the substrate (though, not necessarily in contiguous sequence): indium tin oxide film/tin oxide film/film comprising titanium oxide, or: indium tin oxide film/tin oxide film/oxynitride film/film comprising titanium oxide. The film comprising titanium oxide can be, for example, a TiO₂ film or a film comprising both titanium oxide and tungsten oxide (e.g., about 2.5% W). The film comprising titanium oxide can have a physical thickness of less than 200 Å, or even less than 75 Å, such as about 50 Å. In the present embodiments, the film comprising titanium oxide 70 can be the outermost (i.e., exposed) film of the coating 7.

Referring to the embodiments of FIGS. 5-8, the “first” (or “#1”) surface is exposed to an outdoor environment. Accordingly, it is the #1 surface that radiation from the sun first strikes. The external surface of the outboard pane is the so-called first surface. Moving from the #1 surface toward the interior of the building, the next surface is the “second” (or “#2”) surface. Thus, the internal surface of the outboard pane is the so-called second surface. Moving further toward the interior of the building, the next surface is the “third” (or “#3”) surface, followed by the “fourth” (or “#4”) surface. This convention is carried forward for IG units having more than four major pane surfaces. Thus, for a triple-pane IG unit, the #6 surface would be the external surface of the inboard pane.

One group of embodiments provides a triple glazing (e.g., an IG unit having three panes), and coating 7 is provided on the #6 surface of the glazing. In embodiments of this nature, the #1 and/or #2 surfaces may have other functional coatings. The #1 surface, for example, may also have a transparent electrically conductive coating 7′, and/or the #2 surface may have a silver-based low-emissivity coating.

In some cases, the substrate 10′ is heated prior to film deposition, during deposition, or both. Additionally or alternatively, the coated substrate 10′ can be heat treated after being coated. If desired, the post-deposition heat treatment (such as glass tempering) can be performed in air. When the coated substrate 10′ is heat treated, defects in the film can be healed and improvement of crystalline structure can occur in the indium tin oxide film 20 without an uncontrollable change in the chemistry of the transparent conductive film 20. The tin oxide film 100, optionally together with one or more overlying films of the nature described above, may provide resistance to oxygen reaching and reacting with the indium tin oxide film 20 so as to cause uncontrollable change in its chemistry during heat treatment. The film materials and thicknesses described herein are believed to be suitable for accomplishing this object.

In certain embodiments, the coating 7 is on a glass pane, and this coated glass pane is heat treated through a process that leaves the coated glass cut-able by conventional glass cutting techniques. The heat treatment, for example, can involve using lower temperature for conversion so as to maintain the stress in the glass such that the coated glass remains cut-able even after the heat treatment.

In FIGS. 5-8, the substrate 10′ is a transparent pane that is part of an IG unit 110. Commonly, the IG unit 110 has an exterior pane 10 and an interior pane 10′ separated by at least one between-pane space 800. A spacer 900 (which can optionally be part of a sash) is provided to separate the panes 10 and 10′. The spacer 900 can be secured to the internal surfaces of each pane using an adhesive or seal 700. In some cases, an end sealant 600 is also provided. In the illustrated embodiments, the exterior pane 10 has an external surface 12 (the #1 surface) and an internal surface 14 (the #2 surface). The interior pane 10′ has an internal surface 16 (the #3 surface) and, in some cases (i.e., when the IG unit is a double-pane unit), an external surface 18 (the #4 surface). In other embodiments, the IG unit 110 has three panes, such that the external surface 18 of the interior pane 10′ is the #6 surface.

The IG unit can optionally be mounted in a frame (e.g., a window sash or frame) such that the external surface 12 of the exterior pane 10 is exposed to an outdoor environment 77 while the external surface 18 of the interior pane 10′ is exposed to a room-side interior environment. Each internal surface of the unit is exposed to a between-pane space 800 of the IG unit. In some embodiments, the IG unit 100 is a vacuum IG unit.

The IG unit 110 includes a transparent electrically conductive coating 7 in accordance with any embodiment described herein. In the embodiment of FIG. 5, the external surface 18 of pane 10′ bears a transparent electrically conductive coating 7. Here, the illustrated coating 7 is exposed to an environment (in some cases, a temperature-controlled living space) inside a home or another building.

The IG unit 110 can further include one or more films comprising titanium oxide 70, such as a hydrophilic and/or photocatalytic film. In the embodiment of FIG. 7, for example, a film comprising titanium oxide 70 is provided on the external surface 12 of pane 10, so as to be exposed to an outdoor environment 77 (and thus in periodic contact with rain). The film comprising titanium oxide 70 can be part of a photocatalytic and/or hydrophilic coating. If desired, the IG unit 110 can bear two films comprising titanium oxide, e.g., one such film 70 on the external surface 12 of pane 10 and another such film 70 over the rest of the coating 7 on the external surface 18 of pane 10′.

Thus, in some cases, there are two films comprising titanium oxide 70 on the IG unit. When provided, these two coatings may be different. For example, the external surface of the outboard pane and the external surface of the inboard pane can both have photocatalytic films, but they can be different (e.g., in terms of thickness or composition). For example, a photocatalytic film on the external surface of the inboard pane can be adapted for activation by indoor light, while a photocatalytic film on the external surface of the outboard pane may require direct sunlight for activation. More generally, the indoor photocatalytic film may have a higher level of photoactivity (e.g., it may be thicker or have a more highly photoactive composition) than the outside photocatalytic film. When provided, the films comprising titanium may, of course, be applied over one or more other films.

The IG unit 110 may also include one or more low-emissivity coatings 80. In the embodiment of FIG. 8, the IG unit includes a low-emissivity coating 80 on the internal surface 14 of pane 10. When provided, the low-emissivity coating 80 preferably includes at least one silver-inclusive film, which preferably contains more than 50% silver by weight (e.g., a metallic silver film). If desired, a low-emissivity coating 80 can alternatively be on the internal surface 16 of pane 10′. In some embodiments, the coating 80 includes three or more infrared-reflective films (e.g., silver-containing films). Low-emissivity coatings with three or more infrared-reflective films are described in U.S. patent Ser. No. 11/546,152 and U.S. Pat. Nos. 7,572,511 and 7,572,510 and 7,572,509 and Ser. No. 11/545,211 and U.S. Pat. Nos. 7,342,716 and 7,339,728, the salient teachings of each of which are incorporated herein by reference. In other cases, the low-emissivity coating can be a “single silver” or “double silver” low-emissivity coating, which are well-known to skilled artisans.

If desired, the embodiment of FIG. 6 can have a low-emissivity coating on surface 14 or on surface 16. Similarly, the embodiment of FIG. 7 can optionally have a low-emissivity coating on surface 14 or on surface 16.

While the embodiment of FIG. 5 shows the transparent electrically conductive coating 7 being on the #4 surface of an IG unit 110, the #1 surface of the IG unit can alternatively be provided with a transparent electrically conductive coating. In such cases, there can optionally be a low-emissivity coating on surface 14 or on surface 16.

FIG. 6 shows an IG unit 110 having a first transparent electrically conductive coating 7 on the #4 surface of the IG unit, while a second transparent electrically conductive coating 7′ is on the #1 surface of the IG unit. For triple glazed IG units, a first transparent electrically conductive coating can be provided on the #6 surface of the IG unit, while a second transparent electrically conductive coating is provided on the #1 surface of the IG unit. Or, there can simply be a single transparent electrically conductive coating on the #1 surface.

Thus, it can be appreciated that the transparent electrically conductive coating 7 may be provided on one or more of the following IG unit surfaces: the #1 surface, the #4 surface (for a double glazing), and the #6 surface (for a triple glazing). When applied on the #1 surface, the pane will stay warmer and have less condensation. When applied on a #4 or #6 surface, the inboard pane will stay cooler and save energy, but it may catch condensation. In such cases, a hydrophilic and/or photocatalytic coating may be provided over coating 7 so as to encourage rapid evaporation of any condensation that may occur. The transparent electrically conductive coating 7 can also be beneficial for a monolithic glazing, a laminated glass glazing, etc.

The present coating 7 has a number of beneficial properties. The ensuing discussion reports several of these properties. In some cases, properties are reported herein for a single (i.e., monolithic) pane 10′ bearing the present coating 7 on one surface 18 (“the present pane”). In other cases, these properties are reported for a double-pane IG unit 110 having the transparent electrically conductive coating 7 on the #4 surface 18 and a triple silver low-emissivity coating on the #2 surface. The triple silver low-emissivity coating is known commercially as the LoE³-366™ product from Cardinal CG Company. In such cases, the reported properties are for an IG unit wherein both panes are clear 2.2 mm soda lime float glass with a ½ inch between-pane space filled with an insulative gas mix of 90% argon and 10% air (“the present IG unit”). Of course, these specifics are by no means limiting to the invention. For example, the transparent electrically conductive coating can alternatively be provided on the #1 surface of the IG unit, the low-emissivity coating can alternatively be on the #3 surface, the low-emissivity coating can alternatively be a single or double silver low-emissivity coating, etc. Absent an express statement to the contrary, the present discussion reports determinations made using the well-known WINDOW 7.1 computer program (e.g., calculating center of glass data) under NFRC100-2010 conditions.

As already explained, the indium tin oxide 20 is electrically conductive and imparts low sheet resistance in the coating 7. The sheet resistance of the present coating 7 is less than 75 Ω/square. Preferably, the sheet resistance of this coating 7 is 55 Ω/square or less, such as less than 20 Ω/square (e.g., less than 15 Ω/square, less than 14 Ω/square, or even less than 13 Ω/square). The sheet resistance of the coating can be measured in standard fashion using a non-contact sheet resistance meter.

The coating 7 also has low emissivity. The emissivity of the coating 7 is less than 0.75. Preferably, the emissivity is 0.55 or less, such as less than 0.25, less than 0.22, less than 0.2, or even less than 0.18, such as about 0.15. In contrast, an uncoated pane of clear glass would typically have an emissivity of about 0.84.

The term “emissivity” is well known in the present art. This term is used herein in accordance with its well-known meaning to refer to the ratio of radiation emitted by a surface to the radiation emitted by a blackbody at the same temperature. Emissivity is a characteristic of both absorption and reflectance. It is usually represented by the formula: E=1−Reflectance. The present emissivity values can be determined as specified in “Standard Test Method for Emittance of Specular Surfaces Using Spectrometric Measurements,” NFRC 301-2010, the entire teachings of which are incorporated herein by reference.

In addition to low sheet resistance and low emissivity, the U Value of the present IG unit 110 is very low. As is well known, the U Value of an IG unit is a measure of the thermal insulating property of the unit. The smaller the U value, the better the insulating property of the unit. The U Value of the present IG unit is less than 0.35 (i.e., center of glass U value), preferably less than 0.3, more preferably less than 0.25, and perhaps optimally less than 0.24, such as from 0.20-0.23.

The term U Value is well known in the present art. It is used herein in accordance with its well-known meaning to express the amount of heat that passes through one unit of area in one unit of time for each unit of temperature difference between a hot side of the IG unit and a cold side of the IG unit. The U Value can be determined in accordance with the standard specified for U_(winter) in NFRC 100-2014, the teachings of which are incorporated herein by reference.

A tradeoff is sometimes made in low U value coatings whereby the film(s) selected to achieve a low U value have the effect of decreasing the visible transmittance to a lower level than is desired and/or increasing the visible reflectance to a higher level than is ideal. As a consequence, windows bearing these coatings may have unacceptably low visible transmission, a somewhat mirror-like appearance, or suboptimal color properties.

In combination with the beneficial properties discussed above, the present coating 7 has good optical properties. As noted above, a tradeoff is sometimes made in low U value coatings whereby the films selected to achieve a low U value have the effect of restricting the visible transmission to a level that is lower than ideal.

To the contrary, the present coating 7 provides a good combination of these properties. For example, the present IG unit 110 (and the present pane 10′, whether monolithic or as part of the IG unit 110) has a visible transmittance T_(v) of greater than 0.5 (i.e., greater than 50%). Preferably, the present IG unit 110 (and the present pane 10′, whether monolithic or insulated) achieves a visible transmittance T_(v) of greater than 0.55 (i.e., greater than 55%), or greater than 0.60 (i.e., greater than 60%), such as about 0.63.

Further, if the triple silver low-emissivity coating is replaced with a double silver low-emissivity coating like the LoE²-270™ or LoE²-272™ coatings from Cardinal CG Company, then the present IG unit 110 (and the present pane 10′, whether monolithic or insulated) can exhibit a visible transmittance T_(v) of greater than 0.65 (i.e., greater than 65%), or even greater than 0.67.

Moreover, if the triple silver low-emissivity coating is replaced with a single silver low-emissivity coating like the LoE-180™ coating from Cardinal CG Company, then the present IG unit 110 (and the present pane 10′, whether monolithic or insulated) can exhibit a visible transmittance T_(v) of greater than 0.70 (i.e., greater than 70%), or even greater than 0.75.

While the desired level of visible transmittance can be selected and varied to accommodate different applications, certain preferred embodiments provide a coated pane 10′ having a post-heat-treatment monolithic visible transmission of greater than 80%, greater than 82%, or even greater than 85%.

The term “visible transmittance” is well known in the art and is used herein in accordance with its well-known meaning to refer to the percentage of all incident visible radiation that is transmitted through the IG unit 110. Visible radiation constitutes the wavelength range of between about 380 nm and about 780 nm. Visible transmittance, as well as visible reflectance, can be determined in accordance with NFRC 300-2014, Standard Test Method for Determining the Solar and Infrared Optical Properties of Glazing Materials and Fading Resistance of Systems. The well-known WINDOW 7.1 computer program can be used in calculating these and other reported optical properties.

The present coating 7 can provide a visible absorption of less than 10%. Preferably, the visible absorption is less than 5% (e.g., after heat treatment).

The present coating 7 can achieve desirable reflected color properties in combination with excellent thermal insulating properties. For example, the present IG unit 110 preferably exhibits an exterior reflected color characterized by an “a” color coordinate of between −7 and 2 (e.g., between −5 and 1, such as about −1.9) and a “b” color coordinate of between −9 and 0 (e.g., between −6 and −1, such as about −3.4).

The present discussion of color properties is reported using the well-known color coordinates of “a” and “b.” In more detail, these color coordinates result from conventional use of the well-known Hunter Lab Color System (Hunter methods/units, Ill. D65, 10 degree observer). The present color properties can be determined as specified in ASTM Method E 308, the relevant teachings of which are incorporated herein by reference.

In certain embodiments, the foregoing color properties are provided in combination with the sheet resistance, emissivity, U value, and visible transmission properties reported above. For example, the following chart depicts preferred combinations of properties in accordance with certain embodiments (the tabulated properties are after heat treatment).

preferred more preferred Sheet resistance less than 20 Ω/square less than 15 Ω/square emissivity less than 0.25 less than 0.18 U value less than 0.3 less than 0.24 T_(vis monolithic) greater than 75% greater than 85%

In one embodiment, a multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that has only one film comprising silver. The film comprising silver preferably contains at least 50% silver by weight. The low-emissivity coating is exposed to a between-pane space of the IG unit. A desired one of the two external pane surfaces bears a coating 7 comprising both an indium tin oxide film 20 and a tin oxide film 100. The tin oxide film 100 is located over the indium tin oxide film 20. In the present embodiments, the indium tin oxide film 20 has a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 Å and 1,600 Å, while the tin oxide film 100 has a thickness of between 90 Å and 1,200 Å, and preferably is devoid of indium oxide. In the present embodiments, the IG unit has a U value of less than 0.25 together with a visible transmission of greater than 75%. In addition, the IG unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 0 and a “b_(h)” color coordinate of between −8 and −1.

In another embodiment, an IG unit includes an internal pane surface bearing a low-emissivity coating that has only two films comprising silver. Preferably, each film comprising silver contains at least 50% silver by weight. The low-emissivity coating is exposed to a between-pane space of the IG unit. A desired one of the two external pane surfaces bears a coating 7 comprising both an indium tin oxide film 20 and a tin oxide film 100. The tin oxide film 100 is located over the indium tin oxide film 20. In the present embodiments, the indium tin oxide film 20 has a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 Å and 1,600 Å, while the tin oxide film 100 has a thickness of between 90 Å and 1,200 Å, and preferably is devoid of indium oxide. In the present embodiments, the IG unit has a U value of less than 0.25 together with a visible transmission of greater than 65%. In addition, the IG unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 0 and a “b_(h)” color coordinate of between −8 and −1.

In still another embodiment, an IG unit includes an internal pane surface bearing a low-emissivity coating that includes three films comprising silver. Preferably, each film comprising silver contains at least 50% silver by weight. The low-emissivity coating is exposed to a between-pane space of the IG unit. A desired one of the two external pane surfaces bears a coating 7 comprising both an indium tin oxide film 20 and a tin oxide film 100. The tin oxide film 100 is located over the indium tin oxide film 20. In the present embodiments, the indium tin oxide film 20 has a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 Å and 1,600 Å, while the tin oxide film 100 has a thickness of between 90 Å and 1,200 Å, and preferably is devoid of indium oxide. In the present embodiments, the IG unit has a U value of less than 0.25 together with a visible transmission of greater than 60%. In addition, the IG unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 1 and a “b_(h)” color coordinate of between −7 and −1.

In the foregoing three embodiments, the IG unit can, for example, be a double-pane unit with coating 7 on the #4 surface and the low-emissivity coating on the #2 surface. Coating 7 can consist of the following layers: silicon dioxide at about 100 Å/ITO (90% In/10% Sn) at about 1,200-1,400 Å/tin oxide at about 150 Å/SiON at about 900 Å. The low-emissivity coating in the first of the foregoing three embodiments can, for example, be a single-silver low-emissivity coating like the commercially available LoE-180™ coating from Cardinal CG Company of Eden Prairie, Minn., USA. The low-emissivity coating in the second of the foregoing three embodiments can, for example, be a double-silver low-emissivity coating like the commercially available LoE²-270™ or LoE²-272™ coatings from Cardinal CG Company. The low-emissivity coating in the third of the foregoing three embodiments can, for example, be a triple-silver low-emissivity coating like the commercially available LoE³-366™ coating from Cardinal CG Company.

The invention provides one particular group of embodiments wherein the coating 7 has an intermediate level of electrical conductivity. In this particular group of embodiments, the tin oxide overcoat layer 100, while preferred, need not always be present. The sheet resistance and emissivity are higher than the preferred and more preferred ranges tabulated above. Specifically, the emissivity ranges from 0.25 to 0.55. The monolithic visible transmission (T_(vis monolithic)) preferably is greater than 75%, more preferably is greater than 80%, and perhaps optimally is greater than 85% (e.g., after heat treatment). The visible absorption preferably is less than 10%, and more preferably is less than 5% (e.g., after heat treatment). In the present embodiments, the indium tin oxide film preferably has a thickness of between 100 Å and 2,000 Å, such as between 100 Å and 1,200 Å. In some of the present embodiments, the thickness of the indium tin oxide film is greater than 100 Å but less than 1,100 Å, less than 750 Å, less than 500 Å, or even less than 300 Å. One exemplary non-heat-treated coating that may be useful for the present embodiments has a layer of ITO on a glass substrate, where the ITO layer has a thickness of about 1,060 Å. In this case, the emissivity is about 0.45. In another example, a heat-treated coating has the following layer stack: glass/ITO at about 170 Å/SnO₂ at about 1.135 Å/SiON at about 560 Å. In this case, the post-heat-treatment emissivity is about 0.5. In still another example, a heat-treated coating has the following layer stack: glass/ITO at about 520 Å/SnO₂ at about 785 Å/SiON at about 560 Å. In this case, the post-heat-treatment emissivity is about 0.31. If desired, a base coat 15 of the nature described previously may be added to any of these film stacks. Additionally or alternatively, a layer comprising titanium oxide may be added.

The invention also provides methods for producing the present coating 7. In preferred embodiments, the films are deposited by sputtering. Sputtering is well known in the present art.

In accordance the present methods, a substrate 10′ having a surface 18 is provided. If desired, this surface 18 can be prepared by suitable washing or chemical preparation. The present coating 7 is deposited on the surface 18 of the substrate 10′, e.g., as a series of discrete layers, as a thickness of graded film, or as a combination including at least one discrete layer and at least one thickness of graded film. The coating can be deposited using any thin film deposition technique that is suitable for depositing the desired film materials at the desired low haze and roughness levels. Thus, the present invention includes method embodiments wherein, using any one or more appropriate thin film deposition techniques, the films of any embodiment disclosed herein are deposited sequentially upon a substrate (e.g., a sheet of glass or plastic). One preferred method utilizes DC magnetron sputtering, which is commonly used in industry. Reference is made to Chapin's U.S. Pat. No. 4,166,018, the teachings of which are incorporated herein by reference. In some cases, the present coatings are sputtered by AC or pulsed DC from a pair of cathodes. HiPIMS and other modern sputtering methods can be used as well.

Briefly, magnetron sputtering involves transporting a substrate 10′ through a series of low pressure zones (or “chambers” or “bays”) in which the various film regions that make up the coating are sequentially applied. To deposit oxide film, the target may be formed of an oxide itself, and the sputtering may proceed in an inert or oxidizing atmosphere. To deposit indium tin oxide, for example, a ceramic indium tin oxide target can be sputtered in an inert or oxidizing atmosphere. Alternatively, the oxide film can be deposited by sputtering one or more metallic targets (e.g., of metallic indium tin material) in a reactive atmosphere. Tin oxide can be deposited by sputtering one or more tin targets in a reactive atmosphere containing oxygen gas. Silicon nitride can be deposited by sputtering one or more silicon targets (which may be doped with aluminum or the like to improve conductivity) in a reactive atmosphere containing nitrogen gas. Silicon oxynitride can be deposited by sputtering one or more silicon targets (which may be doped with aluminum or the like) in a reactive atmosphere containing oxygen and nitrogen gas. Titanium dioxide can be deposited by sputtering one or more titanium targets (which may be doped with tungsten or the like) in a reactive atmosphere containing oxygen gas. The thickness of the deposited films can be controlled by varying the speed of the substrate, by varying the power on the targets, or by varying the ratio of power to partial pressure of the reactive gas.

Following is a non-limiting method for depositing one embodiment of the present coating 7 onto a glass substrate. A pair of rotatable metallic indium-tin targets is sputtered while an uncoated glass substrate is conveyed past the activated targets at a rate of about 115 inches per minute when depositing the ITO film. In this example, the relative weight amounts of the two metals in the sputterable material of the target is: indium 90%, tin 10%. Here, a power of 6 kW is used for the pair of rotary targets. The sputtering atmosphere is 6 mTorr with a gas flow of 992 sccm of argon and 200 sccm of oxygen. The resulting indium tin oxide film has a thickness of about 520 Å. Directly over this ITO film, a tin oxide film is applied. Here, the tin oxide is applied at a thickness of about 785 Å by conveying the glass sheet at about 115 inches per minute past a pair of rotary tin targets sputtered at 20 kW in a 6 mTorr atmosphere with a gas flow of 629 sccm of oxygen and 992 sccm of argon. Directly over the tin oxide film, a silicon oxynitride film is applied at a thickness of about 560 Å by conveying the glass sheet at about 20 inches per minute past a pair of rotary silicon targets (83% Si, 17% Al, by weight) sputtered at 20 kW in a 5 mTorr atmosphere with a gas flow of 120 sccm of oxygen and 790 sccm of nitrogen.

The coated substrate is then heat treated. Various heat treatment processes can be used. For example, the coated substrate can be heat treated on a conventional production tempering line. In tempering, glass is placed in a furnace maintained at about 680-705° C. (preferably controlled to 690-700° C.). The glass is typically held in the furnace for 100-120 seconds with constant movement to better ensure temperature uniformity of the product. This is intended to raise the glass temperature to about 640° C. The glass is then removed from the furnace and placed in a stream of air for about 50 seconds such that the glass is cool enough for an operator to handle. Moreover, as already explained, the substrate can alternatively be heated prior to film deposition, during deposition, or both.

While some preferred embodiments of the invention have been described, it should be understood that various changes, adaptations and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims. 

What is claimed is:
 1. A multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces, a desired one of the two external pane surfaces bearing a coating comprising both an indium tin oxide film and a tin oxide film, the tin oxide film being located over the indium tin oxide film.
 2. The multiple-pane insulating glazing unit of claim 1 wherein the tin oxide film is in contact with the indium tin oxide film.
 3. The multiple-pane insulating glazing unit of claim 1 wherein the tin oxide film has a thickness of between 90 angstroms and 1,200 angstroms.
 4. The multiple-pane insulating glazing unit of claim 3 wherein the thickness of the tin oxide film is between 200 angstroms and 400 angstroms.
 5. The multiple-pane insulating glazing unit of claim 1 wherein the indium tin oxide film has a thickness of between 100 angstroms and 2,000 angstroms together with a sheet resistance of less than 50 ohms/square.
 6. The multiple-pane insulating glazing unit of claim 5 wherein said desired one of the two external pane surfaces is defined by a glass pane coated with said coating, said coated glass pane having a monolithic visible transmission of greater than 75%.
 7. The multiple-pane insulating glazing unit of claim 6 wherein said monolithic visible transmission is greater than 85% in combination with the sheet resistance of the indium tin oxide film being less than 20 ohms/square.
 8. The multiple-pane insulating glazing unit of claim 6 wherein the thickness of the indium tin oxide film is between 1,000 angstroms and 1,600 angstroms.
 9. The multiple-pane insulating glazing unit of claim 8 wherein the sheet resistance of the indium tin oxide film is less than 15 ohms/square.
 10. The multiple-pane insulating glazing unit of claim 1 wherein the coating further includes an oxynitride film, the oxynitride film being located over the tin oxide film.
 11. The multiple-pane insulating glazing unit of claim 10 wherein the oxynitride film comprises oxygen, nitrogen, and aluminum.
 12. The multiple-pane insulating glazing unit of claim 10 wherein the oxynitride film is an exposed outermost film of the coating and has a thickness of between 100 angstroms and 1,300 angstroms.
 13. The multiple-pane insulating glazing unit of claim 12 wherein the oxynitride film comprises silicon oxynitride and has a thickness of between 400 angstroms and 900 angstroms.
 14. The multiple-pane insulating glazing unit of claim 10 wherein the coating further includes a film comprising titanium oxide, the film comprising titanium oxide being located over the oxynitride film.
 15. The multiple-pane insulating glazing unit of claim 14 wherein the film comprising titanium oxide is an exposed outermost film of the coating and has a thickness of between 10 angstroms and 200 angstroms.
 16. The multiple-pane insulating glazing unit of claim 1 wherein the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that includes at least one film comprising silver, the low-emissivity coating being exposed to the between-pane space, the multiple-pane insulating glazing unit having a U value of less than 0.25 together with a visible transmission of greater than 55%.
 17. The multiple-pane insulating glazing unit of claim 16 wherein the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −7 and 2 and a “b_(h)” color coordinate of between −9 and
 0. 18. The multiple-pane insulating glazing unit of claim 1 wherein the tin oxide film is devoid of indium oxide.
 19. The multiple-pane insulating glazing unit of claim 1 wherein the tin oxide film consists of tin oxide.
 20. A coated pane comprising a glass substrate and a coating on the glass substrate, the coating comprising both an indium tin oxide film and a tin oxide film, the tin oxide film being located further from the glass pane than is the indium tin oxide film, the indium tin oxide film having a thickness of between 100 angstroms and 2,000 angstroms, the tin oxide film having a thickness of between 90 angstroms and 1,200 angstroms, the indium tin oxide film having a sheet resistance of less than 20 ohms/square, and the coated pane having a visible transmission of greater than 75%.
 21. The coated pane of claim 20 wherein the tin oxide film is in contact with the indium tin oxide film.
 22. The coated pane of claim 20 wherein all the films of the coating are oxides, nitrides, or oxynitrides.
 23. The coated pane of claim 20 wherein the visible transmittance is greater than 85%.
 24. The coated pane of claim 20 wherein the thickness of the tin oxide film is between 200 angstroms and 400 angstroms.
 25. The coated pane of claim 20 wherein the thickness of the indium tin oxide film is between 1,000 angstroms and 1,600 angstroms and its sheet resistance is less than 15 ohms/square.
 26. The coated pane of claim 25 wherein the visible transmission is greater than 85%.
 27. The coated pane of claim 20 wherein the coating further includes an oxynitride film, the oxynitride film being located over the tin oxide film.
 28. The coated pane of claim 27 wherein the oxynitride film comprises oxygen, nitrogen, and aluminum.
 29. The coated pane of claim 27 wherein the oxynitride film is an exposed outermost film of the coating and has a thickness of between 100 angstroms and 1,300 angstroms.
 30. The coated pane of claim 27 wherein the oxynitride film comprises silicon oxynitride and has a thickness of between 400 angstroms and 900 angstroms.
 31. The coated pane of claim 27 wherein the coating further includes a film comprising titanium oxide, the film comprising titanium oxide being located over the oxynitride film.
 32. The coated pane of claim 31 wherein the film comprising titanium oxide is an exposed outermost film of the coating and has a thickness of between 10 angstroms and 200 angstroms.
 33. The coated pane of claim 20 wherein the coating is devoid of a metal layer.
 34. The coated pane of claim 20 wherein the tin oxide film is devoid of indium oxide.
 35. The coated pane of claim 20 wherein the tin oxide film consists of tin oxide.
 36. A multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces, a desired one of the two external pane surfaces bearing a coating comprising both an indium tin oxide film and a tin oxide film, the tin oxide film being located over the indium tin oxide film, the indium tin oxide film having a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 angstroms and 1,600 angstroms, the tin oxide film having a thickness of between 90 angstroms and 1,200 angstroms, the tin oxide film being devoid of indium oxide, wherein the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that has only one film comprising silver, the film comprising silver containing at least 50% silver by weight, the low-emissivity coating being exposed to the between-pane space, the multiple-pane insulating glazing unit having a U value of less than 0.25 together with a visible transmission of greater than 75%, wherein the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 0 and a “b_(h)” color coordinate of between −8 and −1.
 37. A multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces, a desired one of the two external pane surfaces bearing a coating comprising both an indium tin oxide film and a tin oxide film, the tin oxide film being located over the indium tin oxide film, the indium tin oxide film having a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 angstroms and 1,600 angstroms, the tin oxide film having a thickness of between 90 angstroms and 1,200 angstroms, the tin oxide film being devoid of indium oxide, wherein the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that has only two films comprising silver, each of the two films comprising silver containing at least 50% silver by weight, the low-emissivity coating being exposed to the between-pane space, the multiple-pane insulating glazing unit having a U value of less than 0.25 together with a visible transmission of greater than 65%, wherein the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 0 and a “b_(h)” color coordinate of between −8 and −1.
 38. A multiple-pane insulating glazing unit having a between-pane space and two opposed external pane surfaces, a desired one of the two external pane surfaces bearing a coating comprising both an indium tin oxide film and a tin oxide film, the tin oxide film being located over the indium tin oxide film, the indium tin oxide film having a sheet resistance of less than 20 ohms/square and a thickness of between 1,000 angstroms and 1,600 angstroms, the tin oxide film having a thickness of between 90 angstroms and 1,200 angstroms, the tin oxide film being devoid of indium oxide, wherein the multiple-pane insulating glazing unit includes an internal pane surface bearing a low-emissivity coating that includes three films comprising silver, each of the films comprising silver containing at least 50% silver by weight, the low-emissivity coating being exposed to the between-pane space, the multiple-pane insulating glazing unit having a U value of less than 0.25 together with a visible transmission of greater than 60%, wherein the multiple-pane insulating glazing unit exhibits an exterior reflected color characterized by an “a_(h)” color coordinate of between −6 and 1 and a “b_(h)” color coordinate of between −7 and −1.
 39. A coated pane comprising a glass substrate and a coating on the glass substrate, the coating comprising both an indium tin oxide film and a tin oxide film, the coating having an emissivity in the range of from 0.25 to 0.55, the tin oxide film being located further from the glass pane than is the indium tin oxide film, the indium tin oxide film having a thickness of greater than 100 Å but less than 1,100 Å, the tin oxide film having a thickness of between 90 angstroms and 1,200 angstroms, the coated pane having a visible transmission of greater than 75%. 